login
Primes having only the (decimal) digits 3, 4 and 7.
4

%I #11 Jul 26 2015 01:52:42

%S 3,7,37,43,47,73,337,347,373,433,443,733,743,773,3343,3347,3373,3433,

%T 3733,4337,4373,4447,4733,7333,7433,7477,33343,33347,33377,33773,

%U 34337,34747,37337,37447,37747,43777,44773,44777,47737,47743,47777,73433,73477,74377,74747,77347,77377,77447,77477,77743

%N Primes having only the (decimal) digits 3, 4 and 7.

%H Harvey P. Dale, <a href="/A199347/b199347.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Pri#PrimesWithDigits">Index to entries for primes with digits in a given set</a>

%t Select[Flatten[Table[FromDigits/@Tuples[{3,4,7},n],{n,5}]],PrimeQ] (* _Harvey P. Dale_, Jul 31 2012 *)

%o (PARI) a(n, list=0, L=[3, 4, 7], reqpal=0)={my(t); for(d=1, 1e9, u=vector(d, i, 10^(d-i))~; forvec(v=vector(d, i, [1+(i==1&!L[1]), #L]), isprime(t=vector(d, i, L[v[i]])*u) || next; reqpal & !isprime(A004086(t)) & next; list & print1(t", "); n--|return(t)))}

%Y Cf. A020449 - A020472, A199325 - A199329.

%K nonn,base

%O 1,1

%A _M. F. Hasler_, Nov 05 2011